Analytical collector current density and base transit time models for high-injection regions

Using perturbation theory focused on modulated electric fields due to injected electrons, we derived analytical models for collector current density, J/sub n/, and base transit time, tau /sub B/, for arbitrarily doped bases. These models are the first valid for arbitrary injection levels before the onset of the Kirk effect, and they include existing models as special cases. Our model predicts that tau /sub B/ for the Gaussian-doped base is still smaller than that for the box-doped base even in high-injection regions.<>